When the strings in a conventional stringed musical instrument such as an electric guitar are tightened the neck of the instrument tends to bow slightly. To counteract this string tension a number of techniques have been employed. For example, an adjustable truss rod inserted into the neck may be used to compensate for the string tension and straighten the bowed neck. However, this generates an undesirably large force on the neck and the fret board which it carries. Moreover, in a traditional wood neck guitar the wood may not be equally strong throughout and as a result the neck is not evenly smoothed out by the tightened truss rod.
A further problem which is often encountered in the necks of conventional stringed instruments is the tendency of wooden necks to vibrate at a resonant frequency which is so close to that of the strings that much of the string vibration is dissipated into the neck. As a result of such sympathetic vibrations acoustic quality is distorted and dead spots are exhibited, particularly at low frequencies.
In an attempt to overcome these difficulties a number of guitar necks have recently employed alternative materials such as carbon graphite and forged aluminum and steel. Carbon graphite guitar necks are lightweight and resist bowing when the strings are adjusted. However, such necks lack the feel of natural wood guitar necks and are so stiff that they permit no fine tuning whatsoever. As a result, they are often unsatisfactory for the experienced musician.
Forged necks of aluminum and steel do provide a rigidity and density which resist the unwanted vibrations. However, as with the carbon graphite necks these materials lack the desired feel and fine adjustability of wood necks. Forged necks also exhibit expansion difficulties thus necessitating constant tuning particularly under the heat of stage lights.
An adjustable truss rod has been employed below a dense filler material in the neck. However, because the rod and filler exhibit different coefficients of expansion, as the instrument is used changes in temperature tend to alter curvature of the neck. This can seriously interfere with the use of the instrument.